Scientist documents 50 years of deer behavior

From 1962 to 2011, Alan Harn spent 6,800 hours in the woods from Oct. 1 to Dec. 31 each year recording the behavior of 1,379 male white-tailed deer.

By Chris YoungStaff Writer

Put a scientist in a tree stand in the woods for 50 years, and you likely will get some interesting science in return.

Alan Harn is an archaeologist by trade who is fortunate to hunt not far from his office at Dickson Mounds Museum near Lewistown.

So most mornings during bow season, Harn is in the woods for an hour or so before work, waiting and patiently watching the behavior of the white-tailed deer.

“I’ve been capturing some subjects with my camera,” Harn said. “And other, I guess you would have to say, somewhat less fortunate subjects with my bow.”

From 1962 to 2011, Harn spent 6,800 hours in the woods from Oct. 1 to Dec. 31 each year recording the behavior of 1,379 male white-tailed deer. Nearly all the observations were made from tree stands on two tracts of private timber.

Harn says what he is doing is nothing new.

“Man has been interacting with the white-tailed deer and observing its patterns for about 11,000 years here in Illinois,” he said.

Harn even published his results: “Five Decades at the Scrape: Observations on Variation in Whitetail Breeding Patterns in Illinois.”

A scrape is a patch of earth pawed by a white-tailed deer and marked with its scent to announce its presence. Rubbing, the process of deer rubbing antlers on young trees, performs a similar function.

Clearing up misconceptions

Over a half-century of hunting, Harn has seen some things change and some things stay the same.

Mostly, he has seen the number of deer in Illinois grow.

Harn began recording his observations not long after deer hunting resumed in Illinois. Deer were mostly gone from the state by the early 1900s and numbers were too low to allow hunting until the first modern deer-hunting season in 1957.

During the early years, Harn said he saw one buck for every 15-18 hours in the field. Now he sees one buck every 1.2 hours.

“Expressed another way, in 1962 I saw four bucks that year and they only killed 38 deer total in Fulton County that year,” he said. “I saw 51 bucks last year.”

Until fairly recently, Harn had undisturbed access to his hunting area, with no one else around.

Harn said he was able to document how deer breeding behaviors in the fall follow predictable patterns based on the length of days and the accompanying rise and fall of hormones that initiate and then slowly reduce the breeding season — or rut.

“There are many misconceptions involving the whitetail breeding process that have become part of hunting lore and oral traditions,” Harn said.

“The study has provided conclusive evidence that the triggering of the rut is not related to weather conditions like first frost, the falling barometer or other weather changes or the phases of the moon,” he said.

That deer breeding cycles are tied to moon phases is the “most blatant” misconception,” Harn said.

For years, he said, experts have published hunting calendars that equate deer movement with moon phases.

He documented 156 full moon phases over the duration of his study and there were no breeding activity peaks.

Rut activity occurs in peaks and lulls governed by the times that does are receptive.

“Onset of the breeding cycle is triggered by decreasing sunlight known as ‘photo period,’” Harn said. “Sunlight entering the eye also triggers antler growth the following year in mid-April.

“The pattern hasn’t changed in the past 50 years and it probably hasn’t changed in the past several thousand years.”

Harn said the cycle continues in late spring and early summer when fawns are born.

“Two hundred days after courtship and successful breeding a new biological clock is set ticking in the renewal of life here in the deer woods.”